In a semiconductor manufacturing process, foreign matters and pattern defects become a cause of failure such as defective electrical insulation and short circuits between wires if they exist on a semiconductor substrate (wafer). If miniaturization of semiconductor devices proceeds and fine foreign matters are present accordingly, even finer foreign matters will become causes of defective electrical insulation of its capacitor and destruction of a gate oxide film and the like.
These foreign matters include those that come from moving parts in a semiconductor conveying device, those produced from human bodies, those produced through reaction in a processing device by process gases, those with chemicals and materials mixed therein, etc., all of which are mixed therein in various states.
Likewise, even in a manufacturing process of a liquid crystal display device, it becomes unusable as a display device if foreign matters adhere onto a pattern or some defect takes place therein. This means that the situation is the same even in a printed circuit board manufacturing process. Adherence of foreign matters becomes a cause of short circuits and detective electrical connections in the pattern.
In a prior art, as one technology for detecting finer foreign matters and defects on a semiconductor substrate at high speed and with high sensitivity, there has heretofore been disclosed as described in Patent Document 1, defect inspecting apparatus which irradiates a laser on the semiconductor substrate and thereby detects light scattering from foreign matters produced where the foreign matters adhere onto the semiconductor substrate, and which compares the result of its detection with the result of immediately preceding inspection of a semiconductor substrate of the same type to thereby eliminate false information that might be caused by a pattern, thus providing high sensitivity and high reliability.
A method of avoiding the entrance of a 0th-order diffracted light from a pattern into the entrance pupil of a detection lens by means of laser irradiating means which enables highly sensitive and reliable inspection of foreign matters and defects has been described in Patent Document 2.
Namely, Patent Document 2 has described that a relationship between the elevation angle of illuminating light, its azimuthal angle and the numerical aperture of the detection lens is set so as to satisfy a predetermined condition to thereby avoid the entrance of the zeroth-order diffracted light.
In Patent Document 2 as well, an illuminating lens having a conical curved surface has been used to narrow down an XY plane of illumination incident obliquely with respect to a substrate to be inspected in a Y direction and produce a slit-shaped beam spot collimated in an X direction. The illuminating lens has a section of a flat convex lens whose focal distance changes linearly along its longitudinal direction.